This application relates to the art of electrical components and, more particularly, to such components having two metal surfaces of opposite polarity separated from one another by a dielectric material. The invention is particularly applicable to thermal cutoffs of the type having an electrical lead separated from a conductive housing by a dielectric material, and will be described with specific reference thereto. However, it will be appreciated that the invention has broader aspects, and can be used with other electrical components having electrical leads.
A known type of thermal cutoff includes a conductive housing having an open end receiving a dielectric bushing through which an electrical lead extends. A curable dielectric sealing material is placed over the outer end of the bushing between the lead and housing. The distance between the housing and the lead along the outer surface of the dielectric material is supposed to satisfy the minimum creepage distance required between two metal surfaces of opposite polarity.
It would be desirable to have a simple and economical way of determining whether the minimum creepage distance requirement has been satisfied.